A loss of heterozygosity in >50% of prostate cancer has been noted. Indeed, 30% of prostatic tumors share a loss of chromosomes 16q and/or 10q, suggesting the loss of critical regulatory genes (i.e., tumor suppressors). Therefore, a subtractive hybridization procedure has been used to isolate low abundance mRNA species that are differentially expressed. Use of this approach was begun to identify molecular markers for prostatic cancer. Investigations will now focus upon the molecular and biological characterization of cDNA clones obtained by the above- mentioned technique from the metasatic human prostatic cell lines (LnCaP, Du145, PC3). These may enable genes expressed in prostate cancers to be distinguished from those expressed in benign hypertrophic tissue and in the normal prostate. Additionally, these expressed sequences will be examined for point mutations and other altered forms of expression. Gene amplification of known oncogenes will be sought, as well as for novel genes. Similarly, molecular examination of genes and their products, particularly between early-stage tumor tissues (A-B) and late-stage samples (C-D) may also enable identification of important, differentially- expressed genes that are altered compared to their normal cellular counterparts. Distinctive clones identified in this phase of the investigation can be used to screen and molecularly categorize potentially metastatic prostate cancers by in situ and confocal laser scanning microscopic (CLSM) studies. Improved techniques of this type will make available a variety of new molecular probes that will afford increased sensitivity for early neoplasia, especially when used in conjunction with the polymerase chain reaction (PCR) technique.